At high rotational speeds, known clutch discs can flutter or wobble from side to side, for example, due to turbulent fluid forces buffeting the clutch discs. As the clutch discs flutter, the clutch discs contact clutch pack separator discs, resulting in an undesirable increase in drag torque for a clutch including the clutch discs. Grooves have been added to known clutch discs to address the flutter or wobble problem. However, the grooves have not adequately resolved the flutter or wobble problem.
FIG. 9 is a partial cross-sectional view of known cast aluminum clutch disc 200. Cast aluminum clutch disc 200 includes spline teeth 202 wider than core ring 204 for clutch disc 200. However, cast aluminum clutch discs are more costly to fabricate than stamped steel clutch discs.
FIGS. 10A and 10B are respective cross-sectional views of known clutch discs 300. In FIGS. 10A and 10B, radially inner portions of core ring 302 have been folded over to form spline tooth 304. Thus, core ring 302 and portions 304A and 304B of tooth 304 have a same thickness 306. The 180 degree bend required to form portions 304A and 304B stresses tooth 304, in particular at rounded ends 304C, reducing the durability of tooth 304. In FIG. 10A, tooth 304 is axially asymmetrical with respect to ring 302, for example, all of portion 304A is radially aligned with ring 302 and portion 304B extends past ring 302 in axial direction AD. In FIG. 10B, portions 304A and 304B are axially centered (symmetrical) with respect to ring 302; however, thickness 306 has been reduced. Reducing thickness 306 reduces the durability of disc 300. Further, rounded ends 304C of teeth 304 reduce the area of sides 308 and 310 parallel to ring 302 and in contact with a hub or other clutch component in which disc 300 is installed. Reducing the area reduces the stability of disc 300 in a clutch and increases the likelihood of disc 300 fluttering or wobbling. Increasing the area of sides 308 and 310 in contact with the hub or other clutch component, by increasing the depth of a groove receiving tooth 304, increases the cost of fabricating the hub or other component and may compromise the durability of the hub or other clutch component.